The present invention proceeds from a device for locks and other locking mechanisms, safety mechanisms and the like, for permitting authorized access to buildings, rooms, motor vehicles and the like, in accordance with the preamble of the main claim.
Safety mechanisms capable of distinguishing between authorized and unauthorized access to buildings, motor vehicles and the like, of preventing the removal of objects and/or of activating or deactivating alarm systems, either simultaneously or otherwise, have been known in many different forms, from usual bit locks, in particular in the form of cylinder locks, to the so-called electronic locks which operate through the entry and evaluation of pre-determined codes.
The known systems discussed hereafter, in particular as regards the electronic arrangement of locks, cover, therefore, only a selection from the given spectrum.
In order to cause the locking mechanism of the known key lock to be released during an access check, or the like, one has to enter a multi-digit number, whereupon the locking mechanism is released provided the correct number has been entered in the correct order. However, this system provides the risk that accompanying persons may observe the entry and memorize the number so entered. Another problem connected with this system resides in the circumstance that a person may forget such a multi-digit number or enter it incorrectly, in particular when acting under stress, which may provide the disadvantage that, apart from the locking mechanism not being released, even a subsequent entry of the correct number may under certain circumstances be blocked for a pre-determined period of time if the system is equipped to prevent trying out of the correct number. But it has anyway been general usage to note the key number of the key lock in some written form so that the code is always physically available. Finally, such a keyboard must have a certain minimum size and be sufficiently protected against environmental influences which makes a key lock of this type suitable mainly for use in enclosed rooms.
The known magnetic card locks are operated by means of a card comprising a carrier on which data have been magnetically recorded and which is introduced into a reading device. The information contained on the carrier strip is read out and the lock is released when conformity is established between such information and a stored code information.
A certain drawback connected with such magnetic card locks is to be seen, however, in the relatively high expense connected with the reading device, which normally must be provided with an electro-mechanical drive, and the facility with which the information can be erased. For, to erase the information contained on the card, it suffices already to bring or store the card near a strong electromagnetic field. The necessary field strengths are, for example, reached already by loudspeakers or mains transformers of radio receivers. Further, a problem may reside in the fact that it may be impossible to protect the access to the reading device for the card against environmental influences which means that such cards are also mainly suited for use in enclosed rooms and that the magnetic information can be easily changed and, accordingly, copied with the same ease.
Magnetic card locks of the type just described are closely related to locks using inductively readable cards. Their operation is similar to that of magnetic card locks--the code carrier is provided in the middle of the card with a continuous metal film whose surface is subdivided into quadrants. By moving these films past inductive reading heads, the quadrants comprising a hole can be distinguished from those having none. This binary information represents the code which is compared with a firmly stored code. The main disadvantage of this inductively readable card is to be seen in the fact that here again an electromagnetic drive is required which offers certain disadvantages regarding the sensitivity to environmental influences and the operating safety. An advantage of the inductively readable card could be seen in the fact that the information present in a digital form can be processed by computers or microprocessors.
Finally, it is also possible to provide a so-called electronic contact lock, in which both the key and the lock are provided with identical resistance networks, with a predetermined number of junctions that can be tapped. By establishing suitable contacts, certain junctions may be selected and related to the contacts of the key so as to provide a code. The contact to the key is implemented as sensor contact because the contact strip required for scanning the key is to carry potential only during the active phase. When the key is placed on a contact strip, the lock is activated by a sensor strip and the coding of the two networks is compared. In case of conformity over a pre-determined period of time, the lock is released. The main drawback of such an electronic contact lock is to be seen in the required contacts and the relatively complex key which is difficult to produce. Contact irregularities which can never be excluded may also require repeated actuations, and in the long run it is also unavoidable that the contact strip gets contaminated and errors are introduced.
Finally, it is also known to provide a coding on a card in the form of opaque and/or transparent sectors forming data or clock tracks which can be detected by the reading device on infrared basis and compared with the stored correct code. If reading is to be effected without motor-driven insertion, then special measures have to be taken to prevent misinterpretations of the code when the card is inserted arbitrarily.